Kh, Ph & Adding Co2?

[OzMic]

KH @ 120ppm/6.7dKH (120 / 17.86 = 6.7dKH)
pH @ 6.8

From the following table, my CO2 equates to >30ppm;

Low light T8 over 90Ltrs, I thought this would be too high for a low tech set-up, so I should not have the need for DIY CO2 is that correct, or not relevant to CO2 injection???

Should I be concerned about this and lower my CO2 (ie. soften the water to 2 or 3dKH)

Your explanations appreciated.

 

[RadaR]

Sorry, but it doesn't work like that.
That table is assuming you are adding CO2 and it is also assuming that your pH value in relation to the KH is solely due to carbonic acid formed when CO2 dissolves into water.
Forget the tables.


Low light t8? What is the wattage?

 

[OzMic]

Around 1.5 WPG over the 90ltrs.

So that table can be used when CO2 has been injected? What's the best method for measuring CO2 levels both before & after adding CO2?

Cheers.

 

[RadaR]

Around 1.5 WPG over the 90ltrs.

So that table can be used when CO2 has been injected?

In an ideal world if there was nothing else in the water that could change the pH level accept carbonic acid due to CO2 then yes. HOWEVER there is no chance that carbonic acid is the only acid changing the pH in the water. There are so many different factors to consider and various other acids that are bound to be in the water.

What's the best method for measuring CO2 levels both before & after adding CO2?

The best way at the moment that we have for measuring CO2 is the Drop Checker method. See this very good guide.
Drop checkers – How they work


If you provided shading plants such as floating plants or large amazon swords then you might not have to inject CO2. You could just dose a liquid carbon additive, such as Easycarbo.

 

[OzMic]

If you provided shading plants such as floating plants or large amazon swords then you might not have to inject CO2. You could just dose a liquid carbon additive, such as Easycarbo.

Is this due to CO2 volume released from these larger plants?

 

[Truck]

no, it's because the surface plants block out light, and the surface plant's don't require more CO2 because they take it from the air that is in contact with the top of the leaves.

 

[OzMic]

Ok, cheers. Thanks for your help clearing those things up - appreciate your time...

 

[aaronnorth]

If you read that link Radar gave you, it gives you a description as to why the KH/ pH charts don't work.

Even adding NO3 & PO4 can decrease the pH which is why you cannot gaurantee the CO2 level from those tables.